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Where to put Air Eliminator
I have a boiler system that was installed 20 years ago. It was originally installed with one circulator pumping into the boiler. After reading Dan Holohan's Pumping Away book several times, I decided to change some the piping so I could have separate control of several zones. The two story house has old cast iron radiators in all rooms except one that has baseboard slant-fin type radiators. It never did keep up with the rest of the house. I moved the circulator to the outlet of the boiler and added another circulator as a separate zone to the room with the baseboard heat. I also added a Taco 4-zone relay switch and another thermostat to control the one room. The whole system now works as I planned, except when just the one room calls for heat the boiler cycles between 160-180* with a lot of thumping in the boiler the entire time. I think there is air in the system that is I can't get out because there is no air eliminator or air scoop. There is a diaphram expansion tank next to the boiler, I did not change any of that piping. There was a small manual bleed valve on top of the boiler that i replaced with an automatic vent, but that did not make any difference in the noise. There are bleed valves on all of the radiators and on the baseboard piping and I have bled all of those. Any suggestions on what type of air eliminator I need to add and where in the system to put it? The ones I have looked at recommend putting it on the outlet of the boiler before the circulators, but there is no horizontal piping runs to install it.